Raise TypeError when __in-operator used with a Document (#1237)

tests/queryset/queryset.py

@@ -4963,6 +4963,56 @@ class QuerySetTest(unittest.TestCase):
         self.assertEqual(i, 249)
         self.assertEqual(j, 249)
 
+    def test_in_operator_on_non_iterable(self):
+        """Ensure that using the `__in` operator on a non-iterable raises an
+        error.
+        """
+        class User(Document):
+            name = StringField()
+
+        class BlogPost(Document):
+            content = StringField()
+            authors = ListField(ReferenceField(User))
+
+        User.drop_collection()
+        BlogPost.drop_collection()
+
+        author = User(name='Test User')
+        author.save()
+        post = BlogPost(content='Had a good coffee today...', authors=[author])
+        post.save()
+
+        blog_posts = BlogPost.objects(authors__in=[author])
+        self.assertEqual(list(blog_posts), [post])
+
+        # Using the `__in`-operator with a non-iterable should raise a TypeError
+        self.assertRaises(TypeError, BlogPost.objects(authors__in=author.id).count)
+
+    def test_in_operator_on_document(self):
+        """Ensure that using the `__in` operator on a `Document` raises an
+        error.
+        """
+        class User(Document):
+            name = StringField()
+
+        class BlogPost(Document):
+            content = StringField()
+            authors = ListField(ReferenceField(User))
+
+        User.drop_collection()
+        BlogPost.drop_collection()
+
+        author = User(name='Test User')
+        author.save()
+        post = BlogPost(content='Had a good coffee today...', authors=[author])
+        post.save()
+
+        blog_posts = BlogPost.objects(authors__in=[author])
+        self.assertEqual(list(blog_posts), [post])
+
+        # Using the `__in`-operator with a `Document` should raise a TypeError
+        self.assertRaises(TypeError, BlogPost.objects(authors__in=author).count)
+
 
 if __name__ == '__main__':
     unittest.main()